title: Monodisperse NaYbF4:Tm3+/NaGdF4 core/shell nanocrystals with near-infrared to near-infrared upconversion photoluminescence and magnetic resonance properties.
abstract: We report core/shell NaYbF(4):Tm(3+)/NaGdF(4) nanocrystals to be used as probes for bimodal near infrared to near infrared (NIR-to-NIR) upconversion photoluminescence (UCPL) and magnetic resonance (MR) imaging. The NaYbF(4):Tm(3+) nanocrystals were previously reported to produce the intense NIR-to-NIR UCPL peaked at ∼800 nm under excitation at ∼975 nm. We have found that the growth of a NaGdF(4) shell on surface of the NaYbF(4):Tm(3+) nanocrystals results in the increase in the intensity of UCPL of Tm(3+) ions by about 3 times. Unlike biexponential PL decay of NaYbF(4):Tm(3+) nanocrystals, the PL decay of NaYbF(4):Tm(3+)/NaGdF(4) core/shell nanocrystals is single exponential and of longer lifetime due to the suppression of surface quenching effects for Tm(3+) PL. The growth of a NaGdF(4) shell on surface of the NaYbF(4):Tm(3+) nanocrystals also provides high MR relaxivity from paramagnetic Gd(3+) ions contained in the shell. The T1-weighted MR signal of the (NaYbF(4):2% Tm(3+))/NaGdF(4) nanoparticles was measured to be about 2.6 mM(-1)s(-1). Due to the combined presence of efficient optical and MR imaging capabilities, nanoprobes based on NaYbF(4):Tm(3+)/NaGdF(4) fluoride nanophosphors can be considered as a promising platform for simultaneous bimodal PL and MR bioimaging.
authors.affiliation: Institute for Lasers, Photonics, and Biophotonics, The State University of New York at Buffalo, Buffalo, New York 14260, USA.
authors.forename: Guanying
authors.initials: G
authors.lastname: Chen
authors.forename: Tymish Y
authors.initials: TY
authors.lastname: Ohulchanskyy
authors.forename: Wing Cheung
authors.initials: WC
authors.lastname: Law
authors.forename: Hans
authors.initials: H
authors.lastname: Ågren
authors.forename: Paras N
authors.initials: PN
authors.lastname: Prasad
mesh_terms: D007259:Infrared Rays; D008163:Luminescent Measurements / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D013499:Surface Properties